Metal arsonate polymers of Cd, Zn, Ag and Pb supported by 4-aminophenylarsonic acid

Crystal structure of di-benzyl-ammonium hydrogen (4-amino-phen-yl)arsonate monohydrate

The title salt, C14H16N+·C6H7AsNO3 -·H2O or [(C6H5CH2)2NH2][H2NC6H4As(OH)O2]·H2O, (I), was synthesized by mixing an aqueous solution of (4-amino-phenyl)-arsonic acid with an ethano-lic solution of di-benzyl-amine at room temperature. Compound I crystallizes in the monoclinic P21/c space group. The three components forming I are linked via N-H⋯O and O-H⋯O inter-molecular hydrogen bonds, resulting in the propagation of an infinite zigzag chain. Additional weak inter-actions between neighbouring chains, such as π-π and N-H⋯O contacts, involving phenyl rings, -NH2 and -As(OH)O3 functions, and H2O, respectively, lead to a three-dimensional network.

Proton-transfer compounds featuring the unusual 4-arsonoanilinium cation from the reaction of (4-aminophenyl)arsonic acid with strong organic acids

The crystal structures of the 1:1 proton-transfer compounds of (4-aminophenyl)arsonic acid (p-arsanilic acid) with the strong organic acids, 2,4,6-trinitrophenol (picric acid), 3,5-dinitrosalicylic acid, (3-carboxy-4-hydroxy)benzenesulfonic acid (5-sulfosalicylic acid) and toluene-4-sulfonic acid have been determined at 200 K and their hydrogen–bonding patterns examined. The compounds are, respectively, anhydrous 4-arsonoanilinium 2,4,6-trinitrophenolate (1), the hydrate 4-arsonoanilinium 2-carboxy-4,6-dinitrophenolate monohydrate (2), the hydrate 4-arsonoanilinium (3-carboxy-4-hydroxy)benzenesulfonate monohydrate (3) and the partial solvate 4-arsonoanilinium toluene-4-sulfonate 0.8 hydrate (4). The asymmetric unit of 2, a phenolate, comprises two independent but conformationally similar cation-anion pairs and two water molecules of solvation, and in all compounds, extensive inter-species hydrogen–bonding interactions involving arsono O–H···O and anilinium N–H···O hydrogen–bonds generate three-dimensional supramolecular structures. In the cases of 1 and 2, the acceptors include phenolate and nitro O-atom acceptors, with 3 and 4, additionally, sulfonate O-atom acceptors, and with the hydrates 2–4, the water molecules of solvation. A feature of the hydrogen–bonding in 3 is the presence of primary chains extending along (010) through centrosymmetric cyclic R 2 2(8) motifs together with conjoined cyclic R 3 4(12) motifs, which include the water molecule of solvation. The primary hydrogen–bonding in the substructure of 4 involves homomolecular cation–cation arsono O–H···O interactions forming columns down the crystallographic four-fold axis of the unit cell.

Unusual 4-arsonoanilinium cationic species in the hydrochloride salt of (4-aminophenyl)arsonic acid and formed in the reaction of the acid with copper(II) sulfate, copper(II) chloride and cadmium chloride

Structures having the unusual protonated 4-arsonoanilinium species, namely in the hydrochloride salt, C₆H₉AsNO₃⁺·Cl^-, (I), and the complex salts formed from the reaction of (4-aminophenyl)arsonic acid (p-arsanilic acid) with copper(II) sulfate, i.e. hexaaquacopper(II) bis(4-arsonoanilinium) disulfate dihydrate, (C₆H₉AsNO₃)₂[Cu(H₂O)₆](SO₄)₂·2H₂O, (II), with copper(II) chloride, i.e. poly[bis(4-arsonoanilinium) [tetra-μ-chlorido-cuprate(II)]], {(C₆H₉AsNO₃)₂[CuCl₄]}_n, (III), and with cadmium chloride, i.e. poly[bis(4-arsonoanilinium) [tetra-μ-chlorido-cadmate(II)]], {(C₆H₉AsNO₃)₂[CdCl₄]}_n, (IV), have been determined. In (II), the two 4-arsonoanilinium cations are accompanied by [Cu(H₂O)₆]²⁺ cations with sulfate anions. In the isotypic complex salts (III) and (IV), they act as counter-cations to the {[CuCl₄]^2-}_n or {[CdCl₄]^2-}_n anionic polymer sheets, respectively. In (II), the [Cu(H₂O)₆]²⁺ ion sits on a crystallographic centre of symmetry and displays a slightly distorted octahedral coordination geometry. The asymmetric unit for (II) contains, in addition to half the [Cu(H₂O)₆]²⁺ ion, one 4-arsonoanilinium cation, a sulfate dianion and a solvent water molecule. Extensive O-H...O and N-H...O hydrogen bonds link all the species, giving an overall three-dimensional structure. In (III), four of the chloride ligands are related by inversion [Cu-Cl = 2.2826 (8) and 2.2990 (9) Å], with the other two sites of the tetragonally distorted octahedral CuCl₆ unit occupied by symmetry-generated Cl-atom donors [Cu-Cl = 2.9833 (9) Å], forming a two-dimensional coordination polymer network substructure lying parallel to (001). In the crystal, the polymer layers are linked across [001] by a number of bridging hydrogen bonds involving N-H...Cl interactions from head-to-head-linked As-O-H...O 4-arsonoanilinium cations. A three-dimensional network structure is formed. Cd^II compound (IV) is isotypic with Cu^II complex (III), but with the central CdCl₆ complex repeat unit having a more regular M-Cl bond-length range [2.5232 (12)-2.6931 (10) Å] compared to that in (III). This series of compounds represents the first reported crystal structures having the protonated 4-arsonoanilinium species.

Crystal structures and hydrogen bonding in the isotypic series of hydrated alkali metal (K, Rb and Cs) complexes with 4-amino-phenyl-arsonic acid

The structures of the alkali metal (K, Rb and Cs) complex salts with 4-amino-phenyl-arsonic acid (p-arsanilic acid) manifest an isotypic series with the general formula [M₂(C₆H₇AsNO₃)₂(H₂O)₃], with M = K {poly[di-μ₃-4-amino-phenyl-arsonato-tri-μ₂-aqua-dipotassium], [K₂(C₆H₇AsNO₃)₂(H₂O)₃], (I)}, Rb {poly[di-μ₃-4-amino-phenyl-arsonato-tri-μ₂-aqua-dirubidium], [Rb₂(C₆H₇AsNO₃)₂(H₂O)₃], (II)}, and Cs {poly[di-μ₃-4-amino-phenyl-arsonato-tri-μ₂-aqua-dirubidium], [Cs₂(C₆H₇AsNO₃)₂(H₂O)₃], (III)}, in which the repeating structural units lie across crystallographic mirror planes containing two independent and different metal cations and a bridging water mol-ecule, with the two hydrogen p-arsanilate ligands and the second water mol-ecule lying outside the mirror plane. The bonding about the two metal cations in all complexes is similar, one five-coordinate, the other progressing from five-coordinate in (I) to eight-coordinate in both (II) and (III), with overall M-O bond-length ranges of 2.694 (5)-3.009 (7) (K), 2.818 (4)-3.246 (4) (Rb) and 2.961 (9)-3.400 (10) Å (Cs). The additional three bonds in (II) and (III) are the result of inter-metal bridging through the water ligands. Two-dimensional coordination polymeric structures with the layers lying parallel to (100) are generated through a number of bridging bonds involving the water mol-ecules (including hydrogen-bonding inter-actions), as well as through the arsanilate O atoms. These layers are linked across [100] through amine N-H⋯O hydrogen bonds to arsonate and water O-atom acceptors, giving overall three-dimensional network structures.

The coordination complex structures and hydrogen bonding in the three-dimensional alkaline earth metal salts (Mg, Ca, Sr and Ba) of (4-aminophenyl)arsonic acid

(4-Aminophenyl)arsonic acid (p-arsanilic acid) is used as an antihelminth in veterinary applications and was earlier used in the monosodium salt dihydrate form as the antisyphilitic drug atoxyl. Examples of complexes with this acid are rare. The structures of the alkaline earth metal (Mg, Ca, Sr and Ba) complexes with (4-aminophenyl)arsonic acid (p-arsanilic acid) have been determined, viz. hexaaquamagnesium bis[hydrogen (4-aminophenyl)arsonate] tetrahydrate, [Mg(H₂O)₆](C₆H₇AsNO₃)·4H₂O, (I), catena-poly[[[diaquacalcium]-bis[μ₂-hydrogen (4-aminophenyl)arsonato-κ²O:O']-[diaquacalcium]-bis[μ₂-hydrogen (4-aminophenyl)arsonato-κ²O:O]] dihydrate], {[Ca(C₆H₇AsNO₃)₂(H₂O)₂]·2H₂O}_n, (II), catena-poly[[triaquastrontium]-bis[μ₂-hydrogen (4-aminophenyl)arsonato-κ²O:O']], [Sr(C₆H₇AsNO₃)₂(H₂O)₃]_n, (III), and catena-poly[[triaquabarium]-bis[μ₂-hydrogen (4-aminophenyl)arsonato-κ²O:O']], [Ba(C₆H₇AsNO₃)₂(H₂O)₃]_n, (IV). In the structure of magnesium salt (I), the centrosymmetric octahedral [Mg(H₂O)₆]²⁺ cation, the two hydrogen p-arsanilate anions and the four water molecules of solvation form a three-dimensional network structure through inter-species O-H and N-H hydrogen-bonding interactions with water and arsonate O-atom and amine N-atom acceptors. In one-dimensional coordination polymer (II), the distorted octahedral CaO₆ coordination polyhedron comprises two trans-related water molecules and four arsonate O-atom donors from bridging hydrogen arsanilate ligands. One bridging extension is four-membered via a single O atom and the other is eight-membered via O:O'-bridging, both across inversion centres, giving a chain coordination polymer extending along the [100] direction. Extensive hydrogen-bonding involving O-H...O, O-H...N and N-H...O interactions gives an overall three-dimensional structure. The structures of the polymeric Sr and Ba complexes (III) and (IV), respectively, are isotypic and are based on irregular MO₇ coordination polyhedra about the M²⁺ centres, which lie on twofold rotation axes along with one of the coordinated water molecules. The coordination centres are linked through inversion-related arsonate O:O'-bridges, giving eight-membered ring motifs and forming coordination polymeric chains extending along the [100] direction. Inter-chain N-H...O and O-H...O hydrogen-bonding interactions extend the structures into three dimensions and the crystal packing includes π-π ring interactions [minimum ring centroid separations = 3.4666 (17) Å for (III) and 3.4855 (8) Å for (IV)].

Hexaaquamanganese(II) bis[hydrogen (4-aminophenyl)arsonate] tetrahydrate

In the structure of the complex salt formed from the reaction of manganese(II) acetate with (4-aminophenyl)arsonic acid (p-arsanilic acid), [Mn(H2O)6](C6H7AsNO3)2·4H2O, the centrosymmetric Mn(H2O)6coordination polyhedron has slightly distorted octahedral stereochemistry, with the two hydrogen (4-aminophenyl)arsonate anions and the four water molecules of solvation related by inversion. Extensive O—H...O, O—H...N and N—H...O hydrogen bonds link all species, giving an overall three-dimensional supramolecular structure, which also has weak π–π ring interactions [minimum ring-centroid separation = 3.7304 (15) Å]. The structure is isotypic with that of the Mg salt.

The three-dimensional hydrogen-bonded structures in the ammonium and sodium salt hydrates of 4-aminophenylarsonic acid

The structures of two hydrated salts of 4-aminophenylarsonic acid (p-arsanilic acid), namely ammonium 4-aminophenylarsonate monohydrate, NH4(+)·C6H7AsNO3(-)·H2O, (I), and the one-dimensional coordination polymer catena-poly[[(4-aminophenylarsonato-κO)diaquasodium]-μ-aqua], [Na(C6H7AsNO3)(H2O)3]n, (II), have been determined. In the structure of the ammonium salt, (I), the ammonium cations, arsonate anions and water molecules interact through inter-species N-H...O and arsonate and water O-H...O hydrogen bonds, giving the common two-dimensional layers lying parallel to (010). These layers are extended into three dimensions through bridging hydrogen-bonding interactions involving the para-amine group acting both as a donor and an acceptor. In the structure of the sodium salt, (II), the Na(+) cation is coordinated by five O-atom donors, one from a single monodentate arsonate ligand, two from monodentate water molecules and two from bridging water molecules, giving a very distorted square-pyramidal coordination environment. The water bridges generate one-dimensional chains extending along c and extensive interchain O-H...O and N-H...O hydrogen-bonding interactions link these chains, giving an overall three-dimensional structure. The two structures reported here are the first reported examples of salts of p-arsanilic acid.